WateringTimesWatering plan, $19
Syringa x persica, WUCOLS IV

How often to water Persian lilac in California

In July in the Central Valley, established Persian lilac in loam needs a deep watering about every 20 days: about 8.8 gallons each time for a plant 4 feet across, about 3.0 gallons a week. Persian lilac is a deciduous shrub with slender, arching branches and lance-shaped leaves, smaller and more heat tolerant than common lilac. In spring it bears clusters of pale violet flowers with an intoxicating fragrance that draws butterflies. It wants full sun, good air circulation and rich, well-drained, neutral to slightly alkaline soil, and it cannot tolerate soggy ground.

ShrubRated for 4 of 6 zones

How often to water Persian lilac, month by month

Your city
Plant width
4 ft
Your soil

Type your city above and the days between waterings and the gallons appear here, worked out from your city's climate table. Or read the figures by climate zone further down.

Every month, on your water days. The personal plan prints this for Persian lilac and the rest of your yard, on the days your water supplier allows.Get the plan for $19

How this is worked out: established roots fill the top 1.5 feet of soil, and you water again when that soil has dried halfway. Loam soil holds about 1.5 inches of water per foot. Water the whole area the plant covers, and skip a watering after a good soaking rain.

Which soil do you have?

Dig down a few inches, take a handful of moist soil and squeeze it.

  • Sandy: gritty, falls apart when you open your hand, will not form a ball.
  • Loam: forms a soft ball that crumbles when you poke it.
  • Clay: forms a firm, sticky ball and squeezes out into a ribbon between thumb and finger.

Still not sure? Pick loam. Most garden beds sit between sand and clay.

How to measure plant width

A shrub with its width marked from one side to the other and the circle under it shaded blue

Measure across the plant, from the tips of the leaves on one side to the tips on the other.

Water the whole area the plant covers, shown in blue. The gallons here cover that area.

A wider plant means more gallons each watering, not more waterings. While it is young, measure again each spring.

How to tell it needs water

  • Ground dry 4 inches down under the branches in summer signals Persian lilac is ready for a soak
  • Leaves curling and drooping in afternoon heat can indicate thirst
  • Powdery white coating on leaves in late summer points to mildew from poor air flow
  • Yellowing leaves and dieback over soggy soil suggest drainage trouble

How to water it

  • Water under the arching branches with drip or a soaker
  • Soak about a foot down, then let the top few inches dry
  • Plant in full sun in rich, well-drained, neutral to slightly alkaline soil
  • Leave space around it for air to move
  • Prune right after flowering to shape it

Through the seasons

Water a new Persian lilac regularly through its first summer. Established shrubs take deeper, less frequent soaks and handle heat better than common lilac. It is deciduous and blooms in spring on bare to leafing branches. WUCOLS rates Persian lilac low water on the north-central coast and in the Central Valley. In South Inland and the high desert it carries a moderate water rating. WUCOLS marks it as not suited to the south coast or the low desert.

In pots

A young Persian lilac can grow in a large container for a few years. Use a rich, well-drained mix. Water once the top couple of inches are dry, letting excess drain fully. In summer, check every few days, since a pot in full sun dries much faster than garden soil. Empty the saucer. Prune after the spring bloom. In winter, while bare, water only when the mix dries.

1 Your climate zone six WUCOLS zones, each from its own reference city
1.07gal per sq ft in JulyLow water use in the Central Valley zone
A year
6.84 gal per sq ft
Reference
Sacramento climate table
Counts
Plant need, before sprinkler losses
0.761.52.33.00.16JAN0.26FEB0.43MAR0.61APR0.83MAY0.99JUN1.07JUL0.95AUG0.72SEP0.47OCT0.22NOV0.14DEC0.761.52.33.00.16JFM0.61AMJ1.07JAS0.47OND
Gallons per square foot per month, Central Valley. Peak 1.07 in Jul, 6.84 a year.

Monthly water need by climate zone

Persian Lilac: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.150.16–0.780.74–
Feb0.210.26–0.870.93–
Mar0.350.43–1.31.46–
Apr0.470.61–1.611.89–
May0.580.83–1.952.39–
Jun0.640.99–2.292.85–
Jul0.641.07–2.513.04–
Aug0.60.95–2.332.79–
Sep0.50.72–1.862.14–
Oct0.350.47–1.331.46–
Nov0.190.22–0.90.93–
Dec0.120.14–0.680.65–
Year4.86.84–18.4121.27–

How this is worked out: the WUCOLS water rating for each zone times that zone’s climate for the month. A dash means WUCOLS does not rate the plant there. The figures are what the plant uses, before sprinkler losses.

Plants with the same water needs 16

Rated low water in the Central Valley, like Persian lilac. Plants that drink alike can share one valve and one schedule.

LavenderLavandula spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyRosemaryRosmarinus officinalislow water, Central Valley1.07 gal/sq ft in JulyBougainvilleaBougainvillea & spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyOlive TreesOlea europaea ssp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyCrape MyrtleLagerstroemia spp., hybrids & cvs.low water, Central Valley1.07 gal/sq ft in JulyLantanaLantana camara ssp. & cvs.low water, Central Valley1.07 gal/sq ft in JulySalviaSalvia greggii ssp., cvs. & hybridslow water, Central Valley1.07 gal/sq ft in JulyAloeAloe spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulySucculentsEcheveria spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyJunipersJuniperus spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyRussian SagePerovskia spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulySagebrushArtemisia spp. (shrubby)low water, Central Valley1.07 gal/sq ft in JulyWild PrivetLigustrum vulgarelow water, Central Valley1.07 gal/sq ft in JulyCoralberrySymphoricarpos orbiculatus (SHADE)low water, Central Valley1.07 gal/sq ft in JulySydney Golden WattleAcacia longifolialow water, Central Valley1.07 gal/sq ft in JulyBlue Leaf WattleAcacia salignalow water, Central Valley1.07 gal/sq ft in July
Minutes for your sprinklers

Turn this into minutes on your water days

Every city page has a calculator that takes Persian lilac, your sprinkler type and the month, and gives the minutes per water day for that supplier's schedule. Or put it in a zone of the personal watering plan and get all twelve months printed.

Questions people ask

How often should I water Persian lilac in summer?

In July, established Persian lilac in loam needs a deep watering about every 20 days in the Central Valley and about every 9 days in the South Inland zone. Sandy soil holds less water, so waterings come closer together. Clay stretches them. Check the soil before each watering and skip one after a soaking rain.

How much water does Persian lilac need per day?

In July in the Central Valley, established Persian lilac needs about 0.4 gallons a day for a plant 4 feet across and about 1.7 gallons a day for a plant 8 feet across. Give it in deep waterings spread days apart rather than a little every day, so the whole root zone gets wet.

Does watering for Persian lilac change across California?

Yes. WUCOLS rates Persian lilac separately for each of the six California climate zones: low water in the North-Central Coastal zone, low water in the Central Valley zone, not suited to this region in the South Coastal zone, moderate water in the South Inland zone, moderate water in the High and Intermediate Desert zone, not suited to this region in the Low Desert zone. The monthly table above shows how the same rating translates into different gallon amounts as reference evapotranspiration changes.

How is Persian lilac different from common lilac?

It is smaller and more heat tolerant, with arching branches and lance-shaped leaves. Its flowers are pale violet and very fragrant. It is easier in warm climates.

Does Persian lilac attract butterflies?

Yes, its fragrant spring flowers attract butterflies. Plant it near a path or window. Bloom is in spring.

Can Persian lilac be a hedge?

Yes, it makes a good informal hedge. Leave room for air flow between plants. Water the whole row evenly.

Why does my lilac have white powder on the leaves?

That is likely powdery mildew. Improve air circulation and avoid overhead watering. It is not a sign the plant needs water.

Can Persian lilac grow in wet soil?

No, it cannot tolerate soggy, wet conditions. Plant it in well-drained soil. Raise the bed in clay.

More plant watering guides

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Sources